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1
Pearson, Paul Nicholas. "Evolution and phylogeny of Palaeogene planktonic foraminifera." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386154.
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Seears, Heidi. "Biogeography and phylogenetics of the planktonic foraminifera." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11879/.
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The planktonic foraminifera are a highly abundant and diverse group of marine pelagic protists that are ubiquitously distributed throughout the worlds’ oceans. These unicellular eukaryotes are encased in a calcareous (CaCO3) shell or ‘test’, the morphology of which is used to identify individual ‘morphospecies’. The foraminifera have an exceptional fossil record, spanning over 180 million years, and as microfossils provide a highly successful paleoproxy for dating sedimentary rocks and archiving past climate. Molecular studies, using the small subunit (SSU) ribosomal (r) RNA gene are used here to investigate the biogeographical distributions and phylogenetic relationships of the planktonic foraminifera. Biogeographical surveys of two markedly different areas of the global ocean, the tropical Arabian Sea, and the transitional/sub-polar North Atlantic Ocean, revealed significant genotypic variation within the planktonic foraminifera, with some genetic types being sequenced here for the first time. The foraminiferal genotypes displayed non-random geographical distributions, suggestive of distinct ecologies, giving insight into the possible mechanisms of diversification in these marine organisms. The ecological segregation of genetically divergent but morphologically cryptic genetic types could, however, have serious repercussions on their use as paleoproxies of past climate change. Phylogenetic analyses of the foraminifera based firstly on a partial ~1,000 bp terminal 3´ fragment of the SSU rRNA gene, and secondly on the ~3,000 bp almost complete gene supported the hypothesis of the polyphyletic origins of the planktonic foraminifera, which appear to be derived from up to 5 separate benthic ancestral lineages. The almost complete gene is sequenced here in the planktonic taxa for the first time, though amplification was problematic. In a first step to addressing a pressing need for new genetic markers to support data gained from the SSU rRNA gene, a culture system was established for the benthic foraminifera, in order to provide a reliable source of DNA for EST library construction or full genome sequencing. Finally, to overcome difficulties associated with the PCR amplification of the foraminifera, a new lysis buffer and DNA extraction procedure was developed. A highly successful buffer was created, allowing high quality DNA to be extracted from foraminiferal specimens, whilst leaving the delicate calcitic shell intact for morphological reference.
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Coxall, Helen Katherine. "Hantkeninid planktonic foraminifera and Eocene palaeoceanographic change." Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/8efa1d22-0ff8-45a3-9a5c-bd5ea90e266f.
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The morphological and ecologicalevolution of middle-upper Eocene planktonic foraminiferal family Hantkeninidae is investigated in the context of the dramatic palaeoceanographic and climatic changes that marked the transition from Paleogene "greenhouse" to Neogene "icehouse" climatic conditions. Morphometric analysis proves that evolution in family Hantkeninidae was gradual but complex in detail with periods of relative stasis. Multiple lines of evidence demonstrate that Hantkenina evolved from planispiral clavate genus Clavigerinella and not, as was previously believed, from Pseudohastigerina micra. The ancestor of Clavigerinella was probably a low trochospiral form Paragloborotalia sp., which has been recognized for the first time in this study at a number of sites. Trends in chamber inflation, tubulospine angle and the position of the tubulospine on each chamber show the most dramatic evolutionary changes, indicating that these are the most useful characters for taxonomy. These morphological changes correlate well with known palaeoceanographic changes as well as the shift in hantkeninid ecology from a deep to a surface water habitat. Hantkeninids underwent pronounced adaptive evolution in depth habitats during the initial phase of the climatic transition. Lower middle Eocene forms lived in a cool deep-water environment within or below the oceanic thermocline and shifted to warmer surface waters in the late middle Eocene. They evolved in the low latitudes and were primarily. a tropical-subtropical group. The occurrence of Hantkenma australis at relatively high northerly and southerly latitudes during the middle Eocene may record a temporary expansion of warmer water conditions into these regions, possibly representing a hitherto unknown "hyperthermal" event. Clavigerinella is rare in middle Eocene open-ocean sequences but occasionally occurs in relative abundance in other localities (such as on continental margins and oceanic seamounts), suggesting that it was specialized for living in upwelling regions. A revised taxonomy of family Hantkeninidae is presented that reflects new understanding ofhantkeninid evolution. The reconstructed phylogeny demonstrates that the tubulospine-bearing genera Hantkenina and Cribrohantkenina represent a monophyletic clade. Multivariate analysis suggests that more than one morphological population existed at several times and that these may represent biological species. The results demonstrate that the hantkeninids are not merely passive recorders of ocean conditions but have instead evolved morphology and changed habitat in response to climate change.
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Barker, S. "Planktonic foraminiferal proxies for temperature and pCO2." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596364.
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The thesis aims to describe developments in the uses of planktonic foraminiferal calcite for oceanographic applications, specifically Mg/Ca ratios and foraminiferal shell weights as proxies for calcification temperature and paleo-pCO2 respectively. Sample preparation for the analysis of Mg/Ca and Sr/Ca ratios in foraminiferal calcite is investigated with the aim of defining a method that will give reproducible results and minimise signal contaminations. Each step of the cleaning procedure is scrutinised in order to gauge which are most important and which may be omitted as unnecessary and potentially detrimental to the elemental measurements being made. Success in the application of Mg/Ca-thermometry depends on the ability to quantify and compensate for any alteration of the primary signal after deposition. Compositional variations in foraminiferal calcite may be associated with partial dissolution at the seaflow. Investigation is made into the excessive scatter observed within a latitudinal transect of core-top Mg/Ca and Sr/Ca ratios and attributed to partial dissolution. Possible means of correcting or minimising the effects of such alteration are investigated and assessed. Recent interest in planktonic foraminiferal shell weight loss as a proxy for dissolution, and as such a potential means of quantifying compositional variability, demands investigation into the possibility that initial shell weight may not be constant. It is demonstrated that considerable variability does occur in the shell weights of several species of planktonic foraminifera in the modern surface ocean. It is proposed that initial shell weight is a function of calcification rate and controlled ultimately by the carbonate ion concentration, [CO3=], of ambient seawater during calcification. A first attempt is made to calibrate the effects of [CO3=] on shell weight in the modern ocean. The potential effects of anthropogenic atmospheric CO2 increases on marine calcification are then synthesised using the mineral relations between [CO3=] and calcification rate.
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Hudson, Wendy. "The evolution and palaeobiogeography of Mesozoic planktonic foraminifera." Thesis, University of Plymouth, 2007. http://hdl.handle.net/10026.1/719.
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In the 1960s Oberhauser and Fuchs (palaeontologists working at the Geologische Bundesanstalt in Vienna) described a range of new taxa from the Triassic of Austria that were thought to be the earliest planktonic foraminifera. The first reactions of the palaeontological community were negative but in the subsequent forty years our knowledge of Jurassic planktonic foraminifera has expanded considerably. A thorough re-evaluation of the Oberhauser and Fuchs collections in Vienna has shown that these species are probably not planktonic and that the first planktonic taxa appeared in the Toarcian. This origination in the centre of Western Tethys was followed by a rapid expansion of planktonic foraminifera throughout Peri-Tethys. This expansion is dominated by the genera Conoglobigerina and Globuligerina and while some believe that their separation is straightforward (based on apertural characters) analysis of large assemblages shows that this differentiation is not reliable and requires further analysis not only of holotypes, paratypes and topotypes but of large assemblages. In Southern Poland, Middle Jurassic limestones in the Pieniny Klippen Belt are described as foraminiferal packstones and represent the first evidence of a foraminiferal ooze on the ocean floor. This indicates that, by the mid-Jurassic, there was an oceanic stratification of the Aragonite and Carbonate Compensation Depths and that the modem ocean system had developed, although the depths of these various layers may have been different to those of the present day. By the Oxfordian a relatively diverse planktonic fauna had expanded throughout Peri- Tethys and, probably, around the globe in the tropics. The fauna expanded further in the early Cretaceous as Gondwana fragmented but data across the important Jurassic to Cretaceous transition is extremely limited and requires further investigation.
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Chapman, Mark Robert. "Late Pliocene planktonic foraminifera : palaeoceanography and faunal evolution." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332388.
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Aze, Tracy. "Cope's rule and macroevolution of Cenozoic macroperforate planktonic foraminifera." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/22350/.
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Abstract A comprehensive phylogeny of macroperforate planktonic foraminifer species of the Cenozoic Era (~65 million years ago to present) is presented. The phylogeny is developed from a large body of palaeontological work that details the evolutionary relationships and stratigraphic (time) distributions of species-level taxa identified from morphology (‘morphospecies’). Morphospecies are assigned to morphogroups and ecogroups depending on test morphology and inferred habitat, respectively. Because gradual evolution is well documented in this clade, instances of morphospecies intergrading over time have been identified, allowing the elimination ‘pseudospeciation’ and ‘pseudoextinction’ from the record and thereby permit the construction of a more natural phylogeny based on inferred biological lineages. Each cladogenetic event is determined as either budding or bifurcating depending on the pattern of morphological change at the time of branching. This lineage phylogeny provides palaeontologically calibrated ages for each divergence that are entirely independent of molecular data. The tree provides a model system for macroevolutionary studies in the fossil record addressing questions of speciation, extinction, and rates and patterns of evolution. Specifically for this thesis the phylogenies provide a statistically robust framework for testing Cope’s rule (the evolutionary trend towards larger body size along a lineage). Eleven case studies were selected at random from all possible Neogene lineages and the mean areas of ancestor and descendant populations were compared. Over 6000 measurements were taken from 30 lineages and the resulting data show that Neogene macroperforate planktonic foraminifera do not support Cope’s rule with only 48% of the ancestor-descendant population comparisons demonstrating an increase in mean area. The size analysis illustrates that the most robust method for testing Cope’s rule is to compare ancestor-descendant populations from the beginning and end of evolutionary lineages as these are the least affected by temporal sampling biases.
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Hathorne, Edmund Charles. "The trace element and lithium isotope composition of planktonic foraminifera." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417477.
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Corfield, Richard Murray. "The environmental control of the evolution of Palaeocene and early Eocene planktonic Foraminifera." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328866.
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Fenton, Isabel. "Environmental controls on planktonic foraminiferal diversity in ancient and modern oceans." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/53930.
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Planktonic foraminifera are unicellular zooplankton, whose calcium carbonate ‘shells’, wide geographic distributions and very large population sizes combine to give them perhaps the best fossil record over the last 66 Ma of any group. Site-level assemblage diversity can be estimated comparably in the Recent and through geological time. In this thesis I model the environmental correlates of coretop (Recent) planktonic foraminiferal diversity (Chapter 2), with the aim of applying the model to the Eocene. Present-day diversity patterns are shaped by a richer combination of factors than suggested by previous work. I assess the potential of several non-biological biases to distort diversity patterns (Chapter 3). Functional and evolutionary diversity are less prone to bias than are species richness and evenness, while water depth has little impact on diversity in sites deeper than 500m. Asexuality has been suggested as an adaptation in low diversity environments. I used NanoCT scans of proloculi to test whether Neogloboquadrina pachyderma, the dominant species in polar waters, contains an asexual morph (Chapter 4), finding no support for this hypothesis. Having dealt with potential sources of bias, I use models from Chapter 2 to predict diversity in another time period, the Eocene (Chapter 5), based on current understanding of Eocene environments. The latitudinal gradient of species richness developed through the Eocene in both planktonic foraminifera and coccolithophores. Predicted and observed diversity fit well in the late – but not the early – Eocene. My analyses support two explanations for the early-Eocene mismatch. First, early Eocene climate model estimates of environment differ from the proxy records (which fit the fossil data better). Second, the intercorrelations among facets of diversity have changed through time (Chapter 6). Despite our limited understanding of some aspects of their biology, planktonic foraminifera have much to offer as a model system for macroevolution.
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Rickaby, Rosalind Emily Mayors. "Planktonic foraminiferal Cd/Ca : a new perspective on Southern Ocean palaeoproductivity." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624523.
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Al-Sabouni, Nadia. "Spatial and temporal size and diversity patterns in neogene-recent planktonic foraminifera." Thesis, Royal Holloway, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498251.
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Poole, C. R. "The late Neogene planktonic foraminifera genus Globigerinoidesella : taxonomy, biostratigraphy, evolution and palaeoecology." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1557291/.
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Planktonic foraminifera have one of the most complete fossil records of any group, and have proved invaluable in the fields of biostratigraphy, palaeoceanography and evolutionary studies. Gradual morphological change characterises their evolution, meaning that species delimitation for biostratigraphic purposes is typically artificial and arbitrary. Delimited taxa in the fossil record are ‘morphospecies’ rather than biological species. The late Neogene morphospecies Globigerinoidesella fistulosa is of considerable biostratigraphic utility because of its short stratigraphic range (mid-Pliocene to early Pleistocene) and unique morphology. It evolved distinctive protuberances on the final chamber(s), but morphospecies delimitation is problematic because of intergradation with its ancestor Trilobatus sacculifer. The fossil record of Globigerinoidesella fistulosa was investigated from multiple ocean basins, with research focused on four main areas: (1) Systematic taxonomy of G. fistulosa and the Trilobatus sacculifer plexus; (2) Biostratigraphy and biochronology of the extinction of G. fistulosa; (3) The role of heterochrony (i.e. changes in the timing and/or rate of development) in the morphological evolution of G. fistulosa; (4) Determination of the palaeoecology of G. fistulosa in relation to its ancestor T. sacculifer, to understand the mode of speciation and the potential palaeoceanographic applications of G. fistulosa. The taxonomic concepts of Globigerinoidesella fistulosa and the Trilobatus sacculifer plexus were revised, resolving numerous taxonomic issues in the group. Protuberance development was found to not only occur in Pliocene-Pleistocene T. sacculifer, but was also observed in Trilobatus immaturus, Trilobatus quadrilobatus and modern T. sacculifer specimens. New ages for the extinction of G. fistulosa and comparison with updated literature ages revealed that the currently used age of 1.88 Ma is only suitable locally and not applicable at other sites worldwide, where the extinction occurred between 1.716 and 1.74 Ma (~150,000 years later). The morphological evolution of G. fistulosa is demonstrated to be an example of the heterochronic process hypermorphosis. Stable isotope analyses (δ13C and δ18O) and palaeobiogeographic data reveal that G. fistulosa was a photosymbiotic, shallow-dwelling morphospecies with a distribution that tracked warm water oceanographic features. Geochemical depth profiles through test walls of G. fistulosa and T. sacculifer generated through laser ablation inductively coupled plasma mass spectrometry show heterogeneous Mg/Ca distribution, including cyclic high and low Mg/Ca banding and low Mg/Ca outer crusts.
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Ravula, Sharath Reddy. "Environmental factors affecting planktonic foraminifera abundance and distribution in the Northeast Gulf of Mexico." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2251.
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The shell composition of planktonic foraminifera used in many paleoreconstructions assumes they are accurately representing conditions at the surface/mixed layer. However, planktonic foraminifera are known to inhabit a depth range that extends below the mixed layer. In the present study, foraminifera were collected at discrete depth intervals using a Multiple Opening and Closing Net Environmental Sensing System (MOCNESS) in either cyclonic or anticyclonic eddies that had contrasting environmental conditions. The foraminifera abundances and distributions were compared to the water depth, temperature, density, and chlorophyll profiles. Nine species were found consistently among all the tows and composed at least 96% of the species found, though a shift in the species abundances and depths occurred between eddies. Species occurred where physical factors were compatible with conditions and feeding opportunities they were adapted to. Three species pink and white Globigerinoides ruber and Globigerinoides sacculifer thrived best when a steep density gradient resulted in a shallower mixed-layer that restricted them under more intense light and allowed them to better exploit their algae symbionts. Globigerina bulloides was found outside its sub-polar habitat because the waters of the cyclones were cool enough (less than 26??C) at the same depths that sufficient chlorophyll was available. Two species Orbulina universa, and Globorotalia menardii were consistently absent in the mixed layer, but tracked deeper chlorophyll concentrations. Three other species were found inconsistently among the tows: Hastigerina pelagica, Globigerinella siphonifera, and Globigerinella calida. H. pelagica probably follows chlorophyll concentrations. G. siphonifera, and G. calida have a preference for deeper waters within the photic zone. The drastic doubling to tripling of the foraminifera abundances in cyclones biases downcore reconstructions of sea surface temperature towards cooler conditions. Also, the shift in species composition between the two eddies indicates that in environments where eddies, upwellings, or rings exist may bias the downcore composition of each species towards cooler conditions. G. sacculifer was found to live primarily in the mixed layer and at least 75% of its downcore individuals are expected to represent conditions there. Researchers should consider the described species distributions to better understand the water column conditions they are reconstructing.
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Gamson, P. "Late Eocene to Early Miocene planktonic foraminifera of the Indian and Atlantic oceans." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303307.
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Lutz, Brendan P. "Late Neogene planktonic foraminifera of the Cibao Valley (Dominican Republic), biostratigraphy and paleoceanography /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1652090801&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Rückheim, Sylvia. "The onset of planktic foraminifera in the mid-Cretaceous of the Boreal Realm." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975763350.
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Majewski, Wojciech. "Middle Miocene warming event and planktonic foraminifera from the Kerguelen Plateau, southern Indian Ocean /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486398528556543.
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Leary, Paul Niell. "The Late Cenomanian anoxic event : implications for foraminiferal evolution." Thesis, University of Plymouth, 1987. http://hdl.handle.net/10026.1/2057.
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This study lnvestigates the effect of the late Cenomanian Oceanic Anoxic Event (OAE) on the planktonic and benthonic foraminifera. On the former, the OAE was the cause of major extinctions within the population, the return to pre-OAE oxygen levels permitting recolonization of the vacated niches. On the latter, the OAE caused extinctions but resulted in a low oxygen tolerant fauna which slowly evolved into the vacated niches on the post-oAE recovery of oxygen levels. The changes in the foraminiferal populations have been integrated With changes in other marine organisms through the late Cenomanian.
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Field, David B. "Planktonic foraminifera in the California current : vertical distributions, decadal climate variability and 20th century warming /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3142453.
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Hurley, John Vincent. "Late-middle Eocene glacioeustacy : evidence from stable isotopes and foraminifera of the the [sic] Planktonic foraminiferan zone P14 (Truncorotaloides rohri zone), Mossy Grove Core, Hinds County, Mississippi." Virtual Press, 1999. http://liblink.bsu.edu/uhtbin/catkey/1117851.
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Glacioeustatic control of a late-middle Eocene oxygen isotope record is evident from the comparison of such a record with an independent proxy for sea-level. The data, δ18O and planktonic:benthic foraminifera ratios, were determined from samples of the Mossy Grove Core, Hinds County, Mississippi. The temporal order of magnitude for the glacioeustatic cycles, while smaller than two other orders of sea level change identified from this sedimentary package, is comparable to those associated with Milankovitch cycles. Refinement of the sample interval’s sequence statigraphy recognizes a Healing Phase Unit and allowed for identification of the time stratigraphic condensed section. Identification of the condensed section allows for the correlation of this sequence to other sections in the Gulf Coast.Department of Geology
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Berberich, Doris. "Die planktische Foraminifere Neogloboquadrina pachyderma (Ehrenberg) im Weddellmeer, Antarktis = The planktonic foraminifere Neogloboquadrina pachyderma (Ehrenberg) in the Weddell Sea, Antarctica /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 1996. http://www.gbv.de/dms/bs/toc/194515826.pdf.
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Alderman, Susan Elizabeth. "Planktonic foraminifera in the sea of Okhotsk : population and stable isotopic analysis from a sediment trap." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/51553.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (leaves 46-53).
by Susan Elizabeth Alderman.
M.S.
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Ni, Yunyan. "Evaluation of boron isotopes and trace element abundances in planktonic foraminifers as palaeo-oceanographic proxies." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431620.
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Hull, Pincelli Marie. "Macroevolutionary patterns in planktonic foraminifera and the recovery of Pelagic Ecosystems from the Cretaceous-Paleogene mass extinction." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3398253.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed May 6, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Kozdon, Reinhard [Verfasser]. "Delta 44/40Ca, Mg-Ca and delta 18O ratios of planktonic foraminifera from the Nordic Seas / Reinhard Kozdon." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019732377/34.
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Amirov, Elnur Fikret. "Planktonic Foraminiferal Biostratigraphy, Sequence Stratigraphy And Foraminiferal Response To Sedimentary Cyclicity In The Upper Cretaceous-paleocene Of The Haymana Basin (central Anatolia, Turkey)." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610140/index.pdf.
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The aim of this study is to establish the planktonic foraminiferal biozonation, to construct the sequence stratigraphical framework and to determine the foraminiferal response to sedimentary cyclicity in the sedimentary sequence spanning Upper Cretaceous-Paleocene in the Haymana basin (Central Anatolia, Turkey).
In order to achieve this study, the stratigraphic section was measured from sedimentary sequence of the Haymana, Beyobasi and YeSilyurt formations. The sedimentary sequence is mainly characterized by flyschoidal sequence that is composed of alternating of siliciclastic and carbonate units.
On the account of the detailed taxonomic study of planktonic foraminifers, the biostratigraphic framework was established for the Maastrichtian-Paleocene interval. The biozonation includes 7 zonesPseudoguembelina hariaensis, P&
#945
, P1, P2, P3, P4 and P5 zones. The Cretaceous-Paleogene (K/P) boundary was delinated between the samples HEA-105 and 106. In order to construct the sequence-stratigraphical framework, the A, B, C and D-type meter-scale cycles were identified. Based on the stacking patterns of them, six depositional sequences, six third and two second order cycles were determined. Third order cycles coincide with the Global Sea Level Change Curve. On the account of the conducted petrographic analysis sandstone, mudstone, marl, limestone and muddy-limestone lithofacies were recorded in the studied samples. In order to demostrate the response of foraminifers to cyclicity, quantitative analysis has been carried out by counting the individuals of planktonic, benthonic foraminifers and ostracods. The best response to sedimentary cyclicity was revealed from planktonic foraminifers. The average abundance of planktonic foraminifers increases in the transgressive systems tract and decreases in the highstand systems tract.
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Swallow, Jane E. "Plio-Pleistocene paleoceanography of the Equatorial Indian Ocean : (quantitative and geochemical analyses of planktonic foraminifera from ODP Hole 709C." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306138.
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Jentzen, Anna [Verfasser], Dirk [Akademischer Betreuer] Nürnberg, and Martin [Gutachter] Frank. "Habitat and geochemical characterization of living planktonic foraminifera in the Caribbean / Anna Jentzen ; Gutachter: Martin Frank ; Betreuer: Dirk Nürnberg." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1236287436/34.
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Lutz, Brendan P. "LATE MIOCENE AND PLIOCENE PALEOCEANOGRAPHY OF THE LOW LATITUDE NORTHERN HEMISPHERE AND ITS IMPLICATIONS FOR FUTURE CLIMATE CHANGE." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/428.
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The late Neogene represents an exceptionally dynamic period in Earth history during which the Northern Hemisphere has transitioned from a warmer, more equable climate to a cooler, more transient state characterized by waxing and waning continental ice sheets. While geographical distal, the tropical ocean has played a significant role in shaping the evolution of the climate system, as the opening and closing of low latitude (LL) ocean gateways and reorganization of oceanic and atmospheric circulation structure have helped shape the climate system into its present form. This study provides a reconstruction of sea surface temperature (SST), ocean circulation, and thermal structure of the LL eastern Pacific and North Atlantic based upon the compilation of proxy data derived from planktic foraminifer assemblages and geochemical techniques. This research begins with a paleoceanographic reconstruction of the eastern tropical Pacific (ETP) and subtropical Northwest Atlantic (NWA) during the early stages of uplift of the Central American Isthmus and associated shoaling of the Central American Seaway (CAS). In the subtropical NWA (DSDP 103 and ODP 1006), the 5.2 to 5.1 Ma interval is characterized by an increase in SST and sea surface salinity, indicating a strengthening of the Florida Current (FC) and Gulf Stream (GS). Sea surface temperature in the ETP Warm Pool (DSDP Site 84) remained relatively stable between 6.9 and 5.1 Ma, during which El Niño-like conditions persisted. A slight cooling is observed after this interval (with synchronous warming in the NWA), followed by the onset of major cooling at ~3.2 Ma, both of which are preceded by a shallowing of the thermocline. Stepwise cooling is attributed to enhanced Atlantic meridional overturn circulation (AMOC), which caused a shoaling of the main tropical thermocline, thereby strengthening the Walker Circulation and weakening the Pacific North Equatorial Counter Current. During the mid-Piacenzian warm period (MPWP; ~3.3-3.0 Ma), SST in the Panama Basin was ~0.8°C cooler than today, while the subtropical NWA was only ~1.1°C warmer. This corroborates evidence for reduced meridional SST gradients during the mid-Pliocene as well as the hypothesis that more vigorous ocean circulation--particularly in the NWA--was critical during this period. The timing of SST changes in the ETP and NWA (~5.1 Ma) suggest that the termination of permanent El Niño and enhanced AMOC did not contribute significantly to the onset of major Northern Hemisphere glaciation (NHG), as both of these events occur well before the beginning of the glacial cycles. However, these processes may have contributed to the development of the small ice sheets of the late Miocene and early Pliocene, but were most likely only preconditioning factors for the onset of major NHG. In contrast, changes in SST and relative thermocline position suggest that high latitude (HL) processes and global cooling may have influenced thermal structure in the ETP. The SST estimates provided indicate that even in its early stages, the shoaling of the CAS had significant implications for low-latitude ocean circulation and thermal structure, as well as for some of the most significant global climate events of the late Neogene, including the MPWP. During the MPWP, mean global surface temperatures were similar to those predicted for the next century (2-3˚ C warmer) while atmospheric CO2 concentrations, paleogeography, and paleobiology were similar to today. As such, the MPWP has been studied in detail as a potential (albeit imperfect) analog for future climate change and has provided a natural and unique test-bed for the integration of proxy data and general circulation models. Central to this research effort is the Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) project, an iterative paleoenvironmental reconstruction of the MP focused on increasing our understanding of warm-period climate forcings, dynamics, and feedbacks by providing three-dimensional data sets for general circulation models. A mainstay of the PRISM project has been the development of a global sea surface temperature (SST) data set based primarily upon quantitative analyses of planktic foraminifer assemblages, supplemented with geochemical SST estimates wherever possible. In order to improve spatial coverage of the PRISM faunal and SST data sets in the LL North Atlantic, this study provides a description of the MP planktic foraminifer assemblage and multiproxy SST estimates from five Ocean Drilling Program sites (951, 958, 1006, 1062, and 1063) in the North Atlantic subtropical gyre (NASG), a region critical to Atlantic Ocean circulation and tropical heat advection. Assemblages from each core provide evidence for a temperature- and circulation-driven 5-10° northward displacement of MP faunal provinces, as well as regional shifts in planktic foraminifer populations linked to species ecology and interactions. General biogeographic trends also indicate that, relative to modern conditions, gyre circulation was stronger (particularly the Gulf Stream, North Atlantic Current, and North Equatorial Current) and meridionally broader. Overall, SST estimates suggest that surface waters in this region were not significantly warmer (1-2˚ C) than today and that mean annual SSTs along LL western boundary currents were indistinguishable from modern. Multiproxy SST data also provide evidence for enhanced northward transport of warm, salty, oligotrophic surface waters via a vigorous western boundary current system with warmer (cooler) cold-season (warm-season) temperatures. Collectively, this reconstruction of SST and ocean circulation provides support for a model of an enhanced Atlantic meridional overturn circulation (AMOC) system, with particularly vigorous LL western boundary currents and thus, more efficient northward heat transport. These trends therefore suggest that more vigorous thermohaline circulation, in conjunction with elevated atmospheric CO2 concentrations, played a significant role in shaping the global surface temperature distribution during the MPWP. A strengthening of the AMOC under warmer-than-modern conditions has significant implications for future climate change. The current generation of climate models suggests that HL warming and associated ice-sheet melting will induce a freshening of the North Atlantic and thus, to a reduction in the strength of the AMOC, thereby buffering surface temperature increases in the Northern Hemisphere. However, if after this transient period of climate system adjustment, Earth returns to a more Pliocene-like climate state the AMOC system may strengthen, thereby exacerbating the HL warmth caused by elevated atmospheric CO2 concentrations. Thus, through the reconstruction of warm-period SST and ocean circulation, this research provides insight into the potential operation of the LL North Atlantic and its associated impact on broad-scale Northern Hemisphere climate.
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Schueth, Jonathan D. Bralower Timothy J. "A multivariate analysis of the recovery of calcareous nannoplankton and planktonic foraminifera from the Cretaceous/Paleogene (K/P) mass extinction." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4730/index.html.
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Stangeew, Elena. "Distribution and isotopic composition of living planktonic foraminifera N. pachyderma (sinistral) and T. quinqueloba in the high latitude North Atlantic." [S.l. : s.n.], 2001. http://e-diss.uni-kiel.de/diss=/=/d464.pdf.
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Weinkauf, Manuel Fritz Gerhard [Verfasser], and Michal [Akademischer Betreuer] Kučera. "The Influence of the Environment on Shell Morphology and Calcification in Planktonic Foraminifera / Manuel Fritz Gerhard Weinkauf ; Betreuer: Michal Kučera." Tübingen : Universitätsbibliothek Tübingen, 2015. http://d-nb.info/1163321265/34.
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Weinkauf, Manuel [Verfasser], and Michal [Akademischer Betreuer] Kučera. "The Influence of the Environment on Shell Morphology and Calcification in Planktonic Foraminifera / Manuel Fritz Gerhard Weinkauf ; Betreuer: Michal Kučera." Tübingen : Universitätsbibliothek Tübingen, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:21-dspace-624610.
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Beukes, Genevieve. "Foraminiferal biostratigraphic studies from Mesozoic succession of selected wells from the Orange Basin, western offshore, South Africa." University of the Western Cape, 2020. http://hdl.handle.net/11394/7594.
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Masters of ScienceLocated on the western offshore on the Atlantic Ocean margin of Southern Africa, the Orange Basin is the youngest and largest of the South Africa’s seven sedimentary basins. This passive margin basin in known for its hydrocarbon potential and therefore is the focus of attraction of several oil exploration companies. The study area lies near the continental margin in which four exploratory wells were drilled. An attempt has been made in this work to understand the depositional settings of these reservoirs and their biostratigraphy. Distribution of important planktonic index foraminifera helps in dating the reservoir sections. Paleoecological studies of benthic foraminifera were used for understanding the prevailing environment during the Cretaceous period. The study indicates that most of the reservoirs are distributed in the Albian (Early Cretaceous) and a few in the Cenomanian age sediments. Relatively shallow shelf sedimentation prevailed in the Late Aptian to middle part of Albian with deposition of arenaceous units. There were periodic localised deepening as well as very shallow depositional condition leading to exposure (diastem) as indicated by lithology and faunal composition. Gradual rise in sea level started in Late Albian and the entire area was under bathyal environment till the end of Cenomanian stage. This is indicated by deposition of claystone rich units and the associated fossil benthics indicates deposition in slope area. The few relatively minor argillaceous sandstone and siltstone units are with poor reservoir quality.
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Herbert, Russel S. "Late Holocene Climatic Change: The little ice age and El Nino from planktonic foraminifera in sediments off walvis bay, South West Africa." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/6568.
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The variation in abundance of the species G. bulloides and G. pachyderma with depth in a core of diatomaceous sediment off Walvis Bay, South West Africa, seems to correlate with the Little Ice Age that occurred during the late Holocene. Although similar research, using species and oxygen isotope variations has been completed in similar sediment off northern Venezuela and in the Santa Barbara Basin (Kipp and Towner 1975, Dunbar 1983), these are the first downcore foraminiferal species records of the South West African deposit. The abundances of some of the minor species, most notably G. ruber, show very distinctive peaks at apparently random intervals. It is thought that these sudden and short-lived increases could be linked to major El-Nino-type events. In order to measure accurately all the down-core foraminiferal changes, we had to develop a chemical solution which dissolves diatoms and organic material without damaging the foraminiferal skeletons. It consists of K2CO3, CaCl2, NaOH and H202 in particular concentrations. By using this technique, it is possible to prevent biassing of the foraminiferal signal during extraction of foraminifera from diatomaceous mud.
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Guray, Alev. "Campanian-maastrichtian Planktonic Foraminiferal Investigation And Biostratigraphy (kokaksu Section, Bartin, Nw Anatolia): Remarks On The Cretaceous Paleoceanography Based On Quantitative Data." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607672/index.pdf.
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The aim of this study is to delineate the Campanian-Maastrichtian boundary by using planktonic foraminifers. In this manner, Kokaksu Section (Bartin, NW Anatolia) was selected and the Akveren Formation, characterized by a calciturbiditic-clayey limestone and marl intercalation of Campanian-Maastrichtian age, was examined. 59 samples were emphasized for position of boundary.
Late Campanian-Maastrichtian planktonic foraminifers were studied in thin section and by washed samples. Two different biostratigraphical frameworks have been established. Globotruncanid zonation consists of Campanian Globotruncana aegyptiaca Zone, Upper Campanian-Middle Maastrichtian Gansserina gansseri Zone and Upper Maastrichtian Abathomphalus mayaroensis Zone, whereas heterohelicids biozonation includes Campanian Pseudotextularia elegans Zone, Lower Maastrichtian Planoglobulina acervuloinides Zone, Middle Maastrichtian Racemiguembelina fructicosa Zone and Upper Maastrichtian Pseudoguembelina hariensis Zone. Campanian-Maastrichtian boundary was determined as the boundary between Pseudotextularia elegans and Planoglobulina acervuloinides zones and Cretaceous-Tertiary boundary was designated by total disappearance of Late Cretaceous forms. Heterohelicid biozonation has been established in this study for the first time in Turkey.
Collecting 300 individuals from each sample, diversity and abundance of assemblages were analyzed in terms of genus and species. ir evaluation of are important in observation of evolutionary trends and ecological changes. Moreover, evolution of different morphotypes is important in this evaluation. Such a study is new in Turkey in terms of examination of responses of planktonic foraminifers to environmental changes.
Taxonomic framework has been constructed to define each species and differences of comparable forms have been discussed. Both scanning electron microscope (SEM) photographs and thin section photographs were used in order to show se distinctions.
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Regenberg, Marcus [Verfasser]. "Inorganic and stable isotope geochemistry of tropical Atlantic, Caribbean planktonic foraminifera : implications for the reconstruction of upper ocean temperatures and stratification / Marcus Regenberg." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019553014/34.
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Kretschmer, Kerstin [Verfasser], Michael [Akademischer Betreuer] Schulz, Michael [Gutachter] Schulz, and Gerold [Gutachter] Wefer. "Global assessment of species-specific habitats of planktonic foraminifera : an ecosystem modeling approach / Kerstin Kretschmer ; Gutachter: Michael Schulz, Gerold Wefer ; Betreuer: Michael Schulz." Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/1153119374/34.
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Weiner, Agnes Katharina Maria [Verfasser], Michal [Akademischer Betreuer] Kucera, and Kate [Akademischer Betreuer] Darling. "Genetic diversity, biogeography and the morpho-genetic relationship in extant planktonic foraminifera / Agnes Katharina Maria Weiner. Gutachter: Michal Kucera ; Kate Darling. Betreuer: Michal Kucera." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072226014/34.
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Mortyn, Peter Graham. "Planktonic foraminifera and upper water column variability in the South Atlantic : a multiple species approach to the deep sea sedimentary record of climate change /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035424.
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Yurco, Lyanne Nadine. "A Multi-Proxy Investigation of the Late Glacial "Mystery Interval" (17.5-14.5 ka)in the Cariaco Basin, Venezuela." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/26.
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The "Mystery Interval" (17.5-14.5 ka) is an unusual time period of abrupt global climate change during the late glacial between Heinrich event 1 and the Bølling-Allerød warm period (~17.5-14.5 ka). This period was characterized by extreme cooling in the North Atlantic region, warming in Antarctica, the rise of atmospheric greenhouse gases, and a variety of hydrologic changes around the globe, all of which may have stemmed from Heinrich event 1 and the possible collapse of the Atlantic?s meridional overturning circulation. A distinctive and unique gray clay layer was deposited in Cariaco Basin, Venezuela, within this time period, which has no apparent counterpart in the basin?s sediment record for at least the last full glacial-interglacial cycle. One hypothesis for the origin of the gray layer is that the initial pulse of deglacial sea level rise over the shallow Unare Platform, south of the basin, caused remobilization and rapid emplacement of previously deposited shelf sediments. However, analysis of the timing and extent of sea level rise as well as evidence from radiocarbon ages and a comparison of the organic content of gray layer sediments and known turbidites in the basin does not support this hypothesis. The alternative hypothesis, that the gray layer is related to increased fluvial discharge from local rivers as a result of elevated regional rainfall, is supported by a number of lines of evidence. The bulk sediment elemental content measured by scanning X-ray fluorescence (XRF) (this study) and clay mineralogy (Yu, 1996) support input of local river sediments. Coccolith abundances (Mertens et al., 2009), sea surface salinity (SSS) estimates and foraminiferal Ba/Ca analysis (this study) are also consistent with freshening of surface waters caused by elevated river runoff. This implies increased rainfall in the region which is corroborated by elemental and mineralogical ratios that point to increased precipitation and chemical weathering. Average terrigenous grain size and terrigenous fluxes are also in line with modern rainy season data. Despite prior suggestions that the Cariaco Basin region should be dry due to a southward-shifted Inter-tropical Convergence Zone (ITCZ) during cool periods in the North Atlantic, such as the Mystery Interval, data presented in this thesis suggest elevated rainfall and fluvial input related to deposition of the gray layer. Multiple lines of proxy evidence indicate that Cariaco Basin may have been characterized by a drier climate in the first part of the Mystery Interval but then shifted to a wetter climate in the second part, after ~16.5 ka, which might resolve this apparent conflict. The change to wetter conditions is most likely due to a northward shift in the position of the ITCZ, possibly due to warming tropical North Atlantic sea surface temperatures (SSTs) and/or extreme North Atlantic seasonality. Comparison of the Cariaco Basin climate records to climate observations from around the globe reveal a similar shift in climatic conditions around the same time, suggesting that the Mystery Interval may actually have been a two-phase event. Although many of the climatic observations from around the world can be explained by a shift from a southerly position of the ITCZ within the first part of the Mystery Interval to a more northerly position during the later part of the interval, many regions are not directly affected by the ITCZ and other complicating factors may play a role in the rapid climate changes observed globally.
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Rebotim, Andreia Seia [Verfasser], Michal [Akademischer Betreuer] Kucera, Michal [Gutachter] Kucera, and Geert-Jan [Gutachter] Brummer. "Ecology and stable isotope geochemistry of modern planktonic foraminifera in the Northeast Atlantic / Andreia Seia Rebotim ; Gutachter: Michal Kucera, Geert-Jan Brummer ; Betreuer: Michal Kucera." Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1176699342/34.
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Rodríguez, Sanz Laura. "Multi-species planktonic foraminiferal Mg/Ca and δ18O as recorders of surface ocean paleoclimatic processes: 2 case studies from diverse oceanographic regions and timescales." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/107952.
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Durante procesos de calcificación los foraminíferos planctónicos incorporan Mg/Ca y fraccionan los isótopos de oxígeno (δ18O) en sus cáscaras dependiendo de la temperatura, y de la temperatura-δ18O de la masa de agua (δ18OSW) donde calcifican, respectivamente. Medidas de Mg/Ca-δ18O en foraminíferos planctónicos han sido ampliamente utilizadas para reconstruir cambios de temperatura y derivar δ18OSW (corregido por el volumen de hielo; δ18OSW-IVC) como proxy de salinidad. Esta tesis utiliza nuevas reconstrucciones de Mg/Ca-temperatura y δ18OSW-IVC para entender cambios en la estructura de la columna de agua durante la Transición del Pleistoceno Medio (MPT; 1250-700 ka) y la Terminación 1 (T1)-Holoceno temprano (20-3 ka) en el Océano Austral y Océano Pacífico, respectivamente. Aunque escalas de tiempos diferentes, ambos fueron períodos de cambios climáticos importantes y entender sus causas es importante para establecer factores que originan la variabilidad natural del clima.
La combinación de procesos físicos y biogeoquímicos en el Océano Austral regulan el intercambio de CO2 entre el océano y la atmósfera durante ciclos glaciales-interglaciales. Reconstrucciones de Mg/Ca-temperatura y δ18OSW-IVC basados en Neogloquadrina pachyderma (sinistral) en la Zona Subantárctica (ODP Site 1090) muestran que al comienzo del MPT (~1250 ka), la expansión de los frentes polares Antárcticos originó el enfriamiento glacial y reducción de salinidad de la superficie del Océano Austral. Se propone que estos cambios conllevaron a la estratificación de la superficie de este océano durante glaciaciones, evitando el intercambio de CO2 con la atmósfera y por lo tanto incrementando el almacenamiento de carbono (C) en profundidad en las glaciaciones siguientes. Adicionalmente se estudió la influencia de la expansión de los frentes polares en la estructura de la columna de agua de la Zona Subantárctica mediante la comparación de registros de Mg/Ca-temperatura y δ18OSW-IVC de foraminíferas planctónicos con profundidades de hábitat distintos; Globigerina bulloides (superficie), N. pachyderma (subsuperficie), and Globorotalii crassaformis (thermoclina). Estos resultados sugieren que la termoclina/haloclina de esa zona se hizo más somera entre 1500-1300 ka probablemente incrementando la disponibilidad de macro-nutrientes en la superficie de la zona. Esto, aunado a la fertilización por Fe durante las glaciaciones del MPT, eventualmente permitió el aumento de productividad observado en la zona, lo cual junto con la estratificación del Océano Austral posiblemente, pudo ocasionar la reducción glacial de pCO2 (~30 ppm) a ~1250 ka. Las condiciones hidrográficas de la parte superficial de la columna de agua fueron también estudiadas Corriente de California (CC, MD02-2505) durante la T1. Se ha sugerido que la formación de aguas profundas en el Atlántico Norte durante el Younger Dryas (YD) y stadial-H1 menguó, incrementando el transporte de calor y salinidad al Océano Austral. Sin embargo sus consecuencias en el Océano Pacífico aún no están bien establecidas. Aquí, reconstrucciones de Mg/Ca-temperatura y δ18OSW-IVC utilizando los morfotipos de Globigerinoides ruber white en el MD02-2505 muestran el calentamiento relativo de la zona debido al debilitamiento de la CC durante la T1 concordando el perfil de δ18OSW-IVC que sugiere condiciones menos salinas hacia el Holoceno. Incrementos pronunciados de δ18OSW-IVC (~0.7‰) durante YD y stadial-H1 aparentemente son consecuencia de un efecto combinado del debilitamiento de la CC y la advección de aguas relativamente más salinas en el Pacífico durante YD y stadial-H1 en respuesta a los cambios en el Atlántico Norte.
Este trabajo enfatiza la respuesta e importancia de las condiciones superficiales de la columna de agua en el sistema climático. En base a reconstrucciones de temperatura y salinidad superficiales se han sugerido mecanismos plausibles de la influencia de las condiciones hidrográficas del Océano Austral en el intercambio de C con la atmósfera durante el MPT y en la respuesta del Océano Pacífico a cambios en el Atlántico Norte durante la T1.During the calcification process planktonic foraminifera incorporate Mg/Ca and fractionate oxygen isotopes (δ18O) in their shells depending on the water mass’ temperature and temperature-seawater δ18O composition (δ18OSW), respectively, where they calcified. Paired Mg/Ca-δ18O measurements in planktonic foraminifera have been widely used as a powerful tool to reconstruct ocean temperature and salinity changes, the latter by deconvolving ice volume corrected δ18OSW (δ18OSW-IVC). This thesis builds on new planktonic foraminiferal Mg/Ca-temperature and δ18OSW-IVC records as proxies to understand past changes in the structure of the water column during the Middle Pleistocene Transition (MPT; 1250-700 ka) and Termination 1 (T1)-early Holocene (20 to 3 ka) focusing on two regions, the Southern Ocean and North-East Pacific Ocean respectively. Although very different timescales, the MPT and T1 were two periods of important climatic changes, the causes and internal feedbacks surrounding’s which are of special interest to assess the drivers of the natural climate variability. A combination of physical and biogeochemical processes in the Southern Ocean regulates the partitioning of CO2 between the ocean and the atmosphere on glacial-interglacial timescales. Neogloquadrina pachyderma (sinistral) Mg/Ca-temperature and δ18OSW-IVC records from a core located in the Subantarctic Zone (ODP Site 1090) have shown that at ~1250 ka, the onset of the MPT, the seaward expansion of the Antarctic ice sheets promoted glacial cooling and freshening of the surface Southern Ocean. We suggest that the glacial freshening could have induced Southern Ocean upper water column stratification and hence hindered the outgassing of respired CO2 to the atmosphere, increasing the storage of C at depth during glacial periods. We further explored changes in the water column structure induced by the expansion of the Antarctic polar fronts by exploiting the different depth habitat preferences of Globigerina bulloides (surface), N. pachyderma (subsurface), and Globorotalii crassaformis (thermocline). Their Mg/Ca-temperature and δ18OSW-IVC reconstructions suggested that the thermocline and halocline of the Subantarctic Zone shoaled from 1500-1300 ka, and persisted as such across the MPT, likely improving macro-nutrient availability in the surface waters. This, in combination with glacial Fe-fertilization, probably allowed the spike in productivity observed during glacial stages in and after the transition. This together with Southern Ocean stratification contributed to the glacial 30 ppm MPT drop in pCO2. The influence of past upper ocean hydrographical changes in the climate system was further studied in a core located in the southern California Current (CC, MD02-2505) across T1. Declining deep water formation in the North Atlantic during Younger Dryas (YD) and stadial-H1 resulted in an increase of heat and salinity transport to the Southern Ocean; however the response of the Pacific Ocean to those changes remains elusive. Mg/Ca-temperature reconstructions inferred from Globigerinoides ruber white morphotypes suggest that the CC weakened across T1, allowing a relative warming of the CC at ~25ºN compared to northern positions. This is further supported by δ18OSW-IVC changes toward fresher conditions into the Holocene. Increases of δ18OSW-IVC (~0.7‰) in tandem with YD and stadial-H1 are suggested to reflect the combined effect of the weakening of the fresh CC and advection of relatively salty water masses to the core in response to the North Atlantic freshening and oceanic reorganization. Overall, this work highlights the role of the upper ocean’s physical properties in the Earth’s climate. Based on temperature and salinity proxy reconstructions we provide plausible mechanisms to explain the role of the Southern Ocean hydrographical conditions in the storage/release of carbon at/from depth during the MPT as well as new insights on the response of the Pacific Ocean to decreases of heat and salinity transport to the North Atlantic within the last period of natural global warming.
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Bonfardeci, Alessandro. "Paleoclimatic and Paleoceanographic reconstruction of the Pleistocene‐ Holocene through the study of planktonic foraminifera of two sedimentary cores collected in North Atlantic Ocean, southwest of the Azores Islands." Thesis, Paris, Muséum national d'histoire naturelle, 2017. http://www.theses.fr/2017MNHN0027.
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Dans le système climatique global, l’océan Atlantique Nord est considéré comme une région très sensible qui joue un rôle crucial pour la dynamique de l’hémisphère nord via la circulation méridienne de retournement de l'océan Atlantique (AMOC), dont fait partie le système de front/courant des Açores. La thèse a pour but d’analyser les interactions hydrographiques et climatiques complexes dans la région des Açores, pour le Pléistocène moyen‐Holocène, par l’analyse des foraminifères planctoniques de deux carottes prélevées en 2013 (Oceanograflu 2013), dans le segment OH1 de la ride médio-atlantique. La thèse est structurée en trois chapitres/articles qui présentent les principaux résultats et leur interprétation. Le premier article a pour but d’établir le modèle d’âge le plus précis possible et de tracer l’histoire de la production/préservation des carbonates dans la région des Açores, au cours du dernier cycle glaciaire. Pour ce faire, les valeurs de carbonate et δ18OG.ruber des deux carottes ont été analysées à haute résolution. Par ailleurs, l’application de la «Modern Analog Technique» à l’analyse des assemblages des foraminifères planctoniques a permis d’estimer les variations de température des eaux de surface (SST-mat). Les courbes d’abondance des espèces résistantes et sensibles à la dissolution ont permis de mettre en évidence d’éventuels intervalles de plus forte dissolution. La partie supérieure de chaque carotte a été datée par spectrométrie de masse (AMS)14C sur les tests de foraminifères. Le modèle d’âge adopté se base également sur la corrélation entre les courbes de δ18OG.ruber et l’enregistrement haute résolution du δ18OG.bulloides de la carotte MD95-2042 (Shackleton et al. 2000) de la marge ibérique, récemment recalibrée en utilisant les données synthétiques LS16 de δ18O (Lisiecki and Stern 2016) relatives aux foraminifères benthiques. L’analyse spectrale a permis de démontrer que les oscillations des valeurs de carbonate et du δ18OG.ruber, lors des derniers 144ka, sont contrôlées par un forçage climatique (orbital et sub-orbital) dans la région des Açores. La comparaison des courbes de carbonate et celles des espèces résistantes à la dissolution, pour les deux carottes situées à des profondeurs différentes, a permis de montrer les variations verticales de la lysocline de la calcite, en particulier lors des évènements de refroidissement plus extrêmes, par exemple à 22,1 kyr avec une remontée de la lysocline de 1000m environ. Le deuxième article essaie de reconstituer la variabilité complexe de l’hydrographie et de la paléoproductivité de l’Atlantique centre Nord lors des derniers 144 kyr grâce à l’analyse des assemblages des foraminifères planctoniques combinée à celle des variations de la température des eaux de surface (SST‐mat). Les fluctuations d’abondance d’espèces actuellement caractéristiques de masses d’eau et/ou des systèmes de front/courant dans l’Atlantique Nord ont été utilisées comme traceurs paléocéanographiques. Cette approche a permis d’évaluer la migration latitudinale/longitudinale du système de front/courant des Açores durant le Quaternaire récent ainsi que celle d’autres fronts et/ou courants caractéristiques de l’Atlantique centre Nord. Le troisième article se focalise sur la variabilité du groupe G. ruber gr. dans la région des Açores. G. ruber a été considéré comme un plexus regroupant plusieurs autres espèces et sous espèces. Plus récemment, des études moléculaires et géochimiques mis en évidence la présence de plusieurs génotypes au sein du plexus G. ruber, ce qui implique l’existence de plusieurs (sous‐) espèces avec des modes de calcification et des préférences écologiques différentes. Malgré l’abondante littérature récente sur ce sujet, les liens entre ces différents génotypes, variants morphologiques, préférences écologiques, et modes de calcification ne sont pas encore très bien compris. (...)In the global climatic system, the North Atlantic Ocean is considered as a highly sensitive region, which plays a crucial role in the Northern Hemisphere dynamics through the so‐called Atlantic Meridional Overturning Circulation (AMOC) system, of which the Azores Front/Current System represents an important part. The main aim of the thesis is to reconstruct the complex hydrographic and climatic interactions in such a climatically‐sensitive area during middle Pleistocene to Holocene through the analysis of the planktonic foraminifera from two cores collected in the OH1 segment of the Mid‐Atlantic Ridge (MAR) south‐westward of the Azores archipelago during the Oceanograflu 2013 cruise. The manuscript is structured in three chapters presenting the major results and their interpretation (...)
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Krahl, Guilherme. "Foraminíferos planctônicos do Paleoceno no testemunho DSDP site 356, platô de São Paulo, Atlântico Sul: bioestratigrafia e inferências paleoecológicas." Universidade do Vale do Rio dos Sinos, 2016. http://www.repositorio.jesuita.org.br/handle/UNISINOS/5711.
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UNISINOS - Universidade do Vale do Rio dos Sinos
O Paleoceno caracteriza-se por um intervalo que sucede o evento de extinção em massa do K/Pg, o qual afetou diversos grupos fósseis. Seu estudo, portanto, revela não apenas padrões sequenciais de radiação evolutiva como processos relacionados à complexa recuperação dos ecossistemas marinhos. Devido a suas características ecológicas os foraminíferos planctônicos são uma importante ferramenta paleoceanográfica para a compreensão da evolução físico-química dos sistemas pelágicos, bem como da evolução do grupo ao longo do Paleoceno. Neste contexto, este trabalho objetiva a caracterização bioestratigráfica e paleoecologica com base em foraminíferos planctônicos paleógenos do testemunho DSDP Site 356 (Leg 39), localizado no Atlântico Sul ocidental.
The Paleocene is characterized by an interval that succeeds the K-Pg mass extinction event which affected several fossil groups. In its study reveals not only a sequential pattern of evolutionary radiation but also processes related to the complex recovery of marine ecosystems. Due to their ecological characteristics the planktonic foraminifera are an important paleoceanographic tool for the understanding of the physicochemical evolution of marine pelagic systems as well as the evolution of the group along the Paleocene. In this context, this paper aims to conduct a biostratigraphic and paleoecological analysis based on Paleogene planktonic foraminifera assemblages (Danian/Seladriano) from the DSDP Site 356 (Leg 39) drilled in the western South Atlantic.
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Junior, Edmundo Camillo dos Santos. "Foraminíferos planctônicos em resposta às mudanças oceanográficas no Atlântico Tropical oeste durante os últimos 30.000 anos." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-25062008-135452/.
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As assembléias dos foraminíferos planctônicos fósseis de dois testemunhos amostrados do Atlântico tropical oeste representativo dos últimos 30.000 anos foram analisadas junto com estimativas de paleotemperatura superficial e ∂18O e ∂13C do foraminífero planctônico Globigerinoides ruber \'branca\'. Estes resultados mostraram que durante o Último Máximo Glacial e durante os eventos de resfriamento de curta duração Heinrich 1 and Younger Dryas o Atlântico tropical oeste manteve altas paleotemperaturas superficiais. Este estudo sugere que durante este período o Atlântico tropical oeste ocorreu uma acumulação de sal e clor nesta porção do Atlântico como conseqüência do enfraqueciemnto do transporte de calor e sal através do equador. Ao final destes eventos a intensificação do transporte de calor e sal foi restabelecido, baixando a temperatura superficial aos valores conhecidos atuamente. Este estudo sugere que o Atlântico tropical oeste atuou como um reservatório de calor e sal durante a deglaciação.The planktonic foraminiferal assemblages of two piston cores from western tropical Atlantic covering the last 30,000 years have been analysed together with paleoceanographic ANN sea surface temperature reconstruction and ?18O and ?13C of the shallow dwelling planntonic foraminifera Globigerinoides ruber \'white\'. These proxies reveal that during the Last Glacial Maximum and during the Heinrich 1 and Younger Dryas cold events, the western tropical experienced warm periods. This study suggest that during these warm intervals a pronounced accumulation of heat and salt occurred at western tropical Atlantic, as a result of cross-equatorial heat and salt transport decrease. At the end of these events, the intensification of cross-equatorial heat and salt transport cooled and freshened the western tropical surface waters. This study suggests the western tropical Atlantic served as a heat and salt reservoir during deglaciation.
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Iwai, Fabiane Sayuri. "Assembléias de foraminíferos planctônicos: Implicações paleoceanográficas nos últimos 450.000 anos em testemunhos do sudoeste do Atlântico Sul." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/21/21133/tde-27072011-104005/.
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O conhecimento das preferências ecológicas de espécies de foraminíferos planctônicos tem sido muito utilizada em investigações paleoceanográficas obtendo bons resultados. O presente estudo realizou inferências sobre as condições oceanográficas das águas superficiais da porção sudoeste do Atlântico Sul nos últimos 450.000 anos através da variação da abundância de foraminíferos planctônicos em dois testemunhos da Bacia de Campos. A partir da Análise de Correspondência foram identificados os três principais fatores responsáveis pela variação dos foraminíferos planctônicos encontrados em cada um dos testemunhos. No testemunho KF-13 os três fatores principais foram interpretados como temperatura, espessura da camada de mistura e sazonalidade; enquanto para o testemunho KF-14 os fatores foram definidos como espessura da camada de mistura, produtividade e sazonalidade. Com esses fatores foram identificados os intervalos de maior intensidade de ventos e produtividade na região. As principais mudanças climáticas do Atlântico Sul encontram-se relacionadas às mudanças de intensidade de ventos e dos sistemas dependentes deles como o Giro Subtropical do Atlântico e a Zona de Convergência Subtropical.Paleoceanographic investigations based on planktonic foraminifera ecologic preferences are widely and succesfully applied. The present study infered surface waters oceanographic conditions from the South Atlantic southwest margin in the past 450.000 years through the planktonic foramifera abundance variation in two cores from Campos Basin. Correspondence Analysis defined three principal factors responsible for the planktonic foraminifera abundance variation in each core. The three KF-13 main factors were interpreted as temperature, mixed layer thickness and sazonality; KF-14 principal factors were defined as mixed layer thickness, productivity and sazonality. These factors made it possible to identify higher wind stress and higher productivity intervals in this region. The main climatic variations in South Atlantic are due to changes in wind stress and the systems which depend on it such as the Atlantic Subtropical Gyre and the Subtropical Convergence Zone.
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Lessa, Douglas Villela de Oliveira. "Variabilidade da ressurgência na região de Cabo Frio (RJ) durante os últimos 1000 anos com base n a associação de foraminíferos Planctônicos." Niterói, 2017. https://app.uff.br/riuff/handle/1/3915.
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Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-06-28T17:17:17Z
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ
Dois box-cores e 15 amostras de sedimento de superfície de fundo foram coletadas na plataforma continental ao largo de Cabo Frio, com o s objetivos de reconstituir a variabilidade do sistema de ressurgência da Água Central do Atlân tico Sul (ACAS) durante o último, milênio utilizando foraminíferos planctônicos; e em um gradiente batimétrico, estudar os efeitos da profundidade sobre a assembléia de foram iníferos planctônicos e bentônicos. Seis espécies de foraminíferos planctônicos foram domina ntes sendo Globigerinoides ruber a mais abundante em todas as amostras. Além de G. ruber , Globoturborotalita rubescens e Globigerinella calida foram associadas à oligotrófica Água Tropical (AT) , enquanto Globigerina bulloides , Turborotalita quinqueloba e Globigerinita glutinata foram associadas à produtiva ACAS. O estudo da assembléia de foramin íferos no gradiente batimétrico revelou um forte aumento da razão planctônico/bentônico (P/ B) com a profundidade a partir de 86 metros, e um crescimento muito acelerado das abundâ ncias absolutas a partir de 110 metros. Também houve uma diferenciação das assembléias de f oraminíferos planctônicos entre profundidades mais rasas (55 – 100 metros) e mais p rofundas (100 – 125 m), sendo que as espécies indicadoras de águas frias e produtivas te nderam a ocupar o intervalo entre as isóbatas de 100 e 115 metros. O perfil BCCF06-03 re gistrou um período de quase 1.200 anos, com taxa de sedimentação variando entre 0,011 a 0,0 32 cm.ano -1 , enquanto o perfil BCCF06- 05 registrou o intervalo entre 960 e 540 anos AP co m taxa de sedimentação constante de 0,025 cm.ano -1 , e três principais fases de produtividade foram ob servadas. Os períodos correspondentes as fase I e II (1160 – 500 anos AP) foram marcados por uma anomalia negativa dos eventos El Niño, sendo que a primeira fase foi a mais produtiva na qual a associação entre G. bulloides e T. quinqueloba indicou ressurgências fortes, associadas a presença de fatores oceanográficos diferentes dos a tuais. Na segunda fase, estes fatores perderam importância, fazendo aumentar a freqüência dos foraminíferos associados a AT. Por fim a fase III (últimos 500 anos) foi caracterizada por um fortalecimento gradual da ressurgência na Pequena Idade do Gelo (PIG), indica das pelo aumento das abundâncias relativas de Neogloboquadrina dutertrei e Globigerina falconensis , no início da PIG e aumento das espécies G. bulloides e G. glutinata no auge da PIG, seguido por uma mudança significativa na oscilação da ressurgência a partir de 170 anos AP. A ressurgência na fase III foi associada a fatores atmosféricos: migração para o sul da Zona de Convergência Intertropical (ZCIT) durante a PIG e um aumento na variabilidade dos eventos El Niño nos últimos 170 anos.
Two box-cores and 15 bottom surface sediment samples were collec ted at continental shelf off Cabo Frio, with the purposes of reconstruct the variability of South Atlantic Central Water (SACW) upwelling system during the last millennium, using planktonic foraminifera; and in the bottom surface sediment, studying the depth eff ects upon benthic and planktonic foraminiferal assemblages. Six planktonic foraminif er’s species were dominant being Globigerinoides ruber the most abundant in all sediment samples. In addi ction to G. ruber , Globoturborotalita rubescens and Globigerinella calida were associated to oligothrophic Tropical Water (TW), while Globigerina bulloides , Turborotalita quinqueloba and Globigerinita glutinata were associated to SACW which is rich in nutrients . The study of foraminiferal assemblages through the bathymetric g radient revealed a strong growth of planktonic/benthic ratio (P/B) from 86 metres to 12 5 metres of depth, and an abrupt growth of absolute abundances starting at 110 metres. There w as also a difference in planktonic foraminiferal assemblages among the 100 and 115 iso baths. The box-core BCCF06-03 covered a period of 1.200 cal years, with sedimenta tion rate varying among 0,011 and 0,032 cm.ano -1 , while the box-core BCCF06-05 covered a period amo ng 960 and 540 cal years BP with constant sedimentation rate of 0,025 cm.ano -1 , and three main phases were observed. The correspondent period to phases I and II (1160 – 500 cal years BP) were marked by a negative anomaly of El Niño events, where the first phase wa s the most productive of box-cores, where the association between G. bulloides and T. quinqueloba indicated strong upwelling, associated to presence of different oceanographic f actors in relation to recent. The second phase, these oceanographic factors lost importance, doing rise the frequency of associated foraminifers to TW. In the latter, phase III (lasts 500 years) was characterized by a gradual strength of upwelling during the Little Ice Age (LI A), indicated by the relative abundances of Neogloboquadrina dutertrei and Globigerina falconensis in the beginning of LIA, and a increasing of G. bulloides and G. glutinata relative abundances at the maximum of LIA, followed by a significative change in the oscillati on from 170 cal years BP. The upwelling in the phase III was associated to atmospheric factors : south migration of Intertropical Convergence Zone (ITCZ) during the LIA, and a incre asing of El Niño events in the lasts 170 years.
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Aquit, Mohamed [Verfasser]. "Late Cretaceous paleoenvironmental evolution and sea-level history of the Tarfaya Basin, SW Morocco : Evidence from XRF scanner-derived elemental records, benthic and planktonic foraminifera and bulk carbonate stable isotopes / Mohamed Aquit." Kiel : Universitätsbibliothek Kiel, 2015. http://d-nb.info/106929005X/34.
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